Simulation study on the impact of check dams on water and sand in Xiliugou Basin and inner Mongolia section of the Yellow River

Severe soil erosion on the Loess Plateau has led to a reduction in the area of agricultural land as well as an increase in the risk of flooding in the lower reaches of the Yellow River. Ten Kongdui (Mongolian for "Kongdui", meaning "Great Mountain Gully") is located in the upper reaches of the arsenic sandstone hilly and gully area. It is located in the heart of the Kubuqi sandstorm area. This area is one of the sandy and coarse sand production areas in the middle reaches of the Yellow River. It is also the main sand source area of the Inner Mongolia section of the Yellow River. The Ten Major Kongdui Xiliugou Basin is located in the upper and middle reaches of the Yellow River in the coarse sand-producing area. The gullies are deep and steep, with exposed arsenic sandstone. The chain reaction of heavy rain, flood and sediment is intense, making it a key channel for coarse sand from the Yellow River to flow into the river. To effectively address soil erosion in this area, curb the expansion of pyrite sandstone gully erosion and reduce the amount of sediment flowing into the Yellow River, it is proposed to establish an integrated engineering system of "soil and water conservation - sediment interception" within the basin. Through the measure of check dam local sediment storage will be achieved, the ecosystem functions will be restored, and the healthy life of the Yellow River will be maintained. Using distributed hydrologic modeling to explore the effects of a sand detention project in the Xiliugou watershed on watershed runoff and sand transport, the SWAT model was calibrated (1990-1999) and validated (2000-2020) using observed runoff and sediment data at Longtouguai Station, the simulated runoff and sand transport at Longtouguai Hydrological Station were found to fit well with the measured values through model simulation. The linear fitting coefficient R² exceeds 0.6, it is considered that the linear relationship between the simulated values and the measured values is reasonable, which indicates that the reservoir model in SWAT model can be used for check dam simulation, and the water and sand impacts of water and sand reduction of the new check dam project on the Xiliugou watershed are analyzed through the results of the SWAT model calculations and the impacts of further calculations on the channel siltation of the Inner Mongolia section of the Yellow River are further calculated. The results show that: 1, the construction of check dams can affect the runoff volume of the basin to a certain extent, and intercepts part of the runoff, the average annual water reduction of the newly built 79 check dams is 2.44 × 10⁶ m³. 2, it has a great influence on the sand transport in the basin, and the effect of sand reduction is obvious, the average annual sand reduction of the newly built 79 check dams is 4.09 × 10⁵ t. 3, Reduces sand content in the Yellow River and enhances flushing of existing sediment in the Nei Mongol section of the river, and reduces water demand for sediment transport. The results of this study provide reference for promoting the construction of water sand replacement project in Xiliugou Basin and the high-quality development of the Yellow River Basin.